Electric clock



June Z3,A- 1953f- P. R. coN'rAN-r Erm.

ELECTRIC CLOCK Filed Dec, 23; 1947 2 Sheets-Sheet 1 June 23, 1953 P. R. coNTAN'r Erm. 2,642,714

- ELECTRIC cLocx rned'pqgzs; 'i'4'7 '2 sheets-sheet 2 y f if). I v, mw N Patented June 23, 1953 ELECTRIC CLOCK Peter R. Contant and Raymond H. Sullivan, Rochester, N. Y., assgnors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application December 23, 1947, Serial No. 793,394

6 Claims.

The present invention relates generally to electric clocks and more particularly to a clock of the electromagnetic impulse type adapted especially for use in automobiles.

The principal object of the invention is to provide certain improvements in the clock construction disclosed in our copending application Serial No. 604,386, filed July 11, 1945, in which a single electromagnet is provided with poles associated with a timing mechanism including a balance wheel armature which controls and is sustained in oscillation by intermittent energization of the electromagnet, and with further poles'associated with a separate driving mechanism including an armature to drive the clock gear train.

In the present clock the balance wheel and as sociated contact mechanism control the energization of the electromagnet to impart a magnetic impulse to the balance wheel once, and for a short period only, of each complete oscillation, and simultaneously impart a magnetic impulse to the driving armature which operates the clock gear train through a pawl and ratchet arrangement.

One feature of the present invention relates li to the construction of the balance wheel and associated parts of the timing mechanism to assure starting of the clock and provide practically constant frequency and amplitude of oscillation of the balance wheel during operation under conditions of varying applied voltage.

Other features involve certain improvements in the contact mechanism associated with the balance wheel armature and in the driving mechanism associated with, the separate driving armature.

Many other features including the construction and relative arrangement of the several parts oi the present clock will be apparent from or speciiically noted in the following description of the embodiment shown in the accompanying drawings.

On the drawings:

Fig. 1 is a bottom plan view of the clock mechanism with the back cover removed.

Fig. 2 is a transverse section taken substantially on line 2-2 of Fig. 1.

Fig. 3 is an enlarged fragmentary section of the driving mechanism taken substantially on line 3 3 of Fig. 1.

Fig. 4 is an enlarged fragmentary section of the contact mechanism taken substantially on line 4--4 of Fig. 1.

Fig. 5 is a diagrammatic view of the balance Wheel with the magnet poles and contact mech- Vf or frame Iii is provided with spaced pillars on 3 ably mounted in the bridge II.

which a bridge II is secured by screws I2, and a pivot staff I3 is journaled between a `iewelled lower bearing I in an offset portion of the frame and a jewelled upper bearing I5 which is adjust- The pivot staff I3 is preferably die cast in a hub I5 die cast in the balance wheel II which also functions as an armature as will be hereinafter described. A hairspring I8 is secured at its inner end to a collet on the hub I6 and is secured at its outer end to a post on the frame I0 With the outer turn of the hairspring passing through a slot in a regulator arm I9. l This arm is connected as shown in Fig. 2 to an operating indicator pointer 2B by a pivot post 2 I, extending through and rotatable in a plate on frame IIJ below the staff I3 to provide for the adjustment of the arm I8 to change the effective length of thehairspring to regulate the period of oscillation of the balance wheel in known manner.

An electrical contact 22 which is preferably of one or more ,of the metals in the rare metal group is die cast in the hub I6 on the pivot staff and provided with a contact portion projecting radially from the hub. The contact portion may be of any desired section but is preferably elliptical as shown in Fig. 4 with the plane of its major axis angularly inclined with respect to the axis of the hub. l

A U-shaped bracket 23 is secured to the frame i6, asshown in Fig. 4, by a screw 24,. and insulated from the frame by washers 25 and bushing 25 of insulating material. The screw 24 is threaded through one leg of the U-shaped bracket and an adjusting screw 2 having a lock nut extends through the other leg in abutting alignment with the end of screw 24 for a purpose to be hereinafter described. LA terminal 2s, spring Contact arm 33, and spring damper arms 3l and (i2A are secured to the bracket 23 by rivets 33. The contact arm V311 is bent upwardly at an angle at its free end and formed with a laterally offset ear 34 which extends toward the pivot stair I3 and is adapted to be engaged by the Contact 22 during oscillation rof the balance wheel. This portion of the arm 3l)I may be made of one or more of the metals in the rare metal group and is provided on its underside with an insulating plate 35 of some hard wearing material such as libre paper which can be bonded to the arm by a suitable adhesive.

The bracket, 23 is formed of; material which is slightly resilient with the legs initially biased toward one another so that the screw 21 can be adjusted to vary the spacing of the legs to adjust the contact arm 3G to position the laterally oniset ear 34 of the contact arm in` the plane of movement of the contact 22. When the contact arm is properly adjusted,v the. cQYlljnQl 242 will alternately engage the upper face of` the ear 311 and the insulating plate 35 during oscillation of the balance wheel.

The contact arm 35 is made of very light, spring material so as to be readily deected from its normal position as the contact 22 engages and slides over either the upper face or the ear 34 or the insulating plate 35, and will tend to oscillate or vibrate when it is released after such deflection. The arms 3| and 32' of very light spring matltl are adapted to dampen this oscillation or vibration of the contact arm. They are located at opposite sides of the contact arm and formed at their free ends with veshaped portions extending toward and arranged to engage the contact. army at spaced points between the ends of this arm. Since the free lengths of these damper arms are direrent and they do not have the same natural period of oscillation and also differ from the natural period of the contact arm,A the contact arm is practically critically damped',l and the construction is such as to impose` only an extremely low mechanical load on the balance wheel as it oscillates during operation.

'I he above deerbed contact mechanism is adapted to control the intermittent energ-ization of the winding of* an electromagnet, indicated generally at tt',y to impart periodic impulsesto both the balance wheel and to a clock driving VNeichanisrn to, be hereinafter described. As shown in Fig. 2 the electromagnet 36 includes a core 31j, a pair or pole pieces 38 and 3?, and a seco nd pair gf pole pieces d and M which are secured together and kto the frame Iii by nuts 42 threaded on the ends oi; the core.V

' .es shown in Figs. 1l and 2l the pole pieces 3B 'and' 33 are so formed as to locate the pole tips in; 'the planeY of the Vbalance wheel Il at points relatively close to the peripheryl thereof so that the` balance wheel functions as an armature in the magnetic field between the pole tips` whenever the electromagnet winding is energized by engagement ofv the contact 2v2-'with the upper face of the ear 34 on contact arm 30. This con tact engagement will occur only during the countercloclgwise movement of the balance wheel as viewed in Fig. 1 and for only a relatively short portion ofv this movement during which the balance wheelreceives a magnetic impulse which is sufficient to sustain it in oscillation as will be more fully described hereinafter with reference to the diagrammatic showing in Figs. 5 to 7', inelusive.

Referring now to the drivingl mechaism for the clock gear train, as shown in Figs. l and 3, the pole pieces 40 and 4| extend parallel to one another and terminate in spaced ends adapted to impart periodic impulses to an armature 3 which is pivotaljly mounted for limited oscillation between the ends of these pole pieces. The

l armature 43 consists ofa U-shaped member of magnetic material which is die cast on a hub 44 together with a shaft e5 which is pivotally mounted in bearing plates 45 and l1 clamped against the sides oi the pole pieces 40 and 4l by retainer plates. 48 and t9.-

A helical spring 56 having one end secured to an outstanding lug 5l on retainer plate :i8 and its other end secured to the armature 3 is adapted to urge the ends of the armature away from the pole pieces di) and 4|. The extent of pivotal movement of the armature is limited by the provision of a slot 52 in the bearing plate 4t to receive the, bent end of a spring wire arm 53 which is fixed at., its other end to the shaft t5 by a collet 54. The spring wire arm 53 also acts as` a buffer to cushion the motion of the armature at both ends of its movement as it is oscillated by being moved in one direction by the spring 50 and in the other direction by magnetic action whenithe electromagnet is energized by the timing mechanism.

A driving pawl in the form or a hairpin spring or spring wire of U-shape, indicated generallyr at 55, is secured to the armature e3 to. oscillate therewith. As shown in Figure 3, this spring is formed with substantially parallel arms or une equal length connected by sev-eral turns or coils to provide the desi-red spring action. The spring 55 is arranged with these arms extending substantially parallel to the axis. of the armature shaft l5- with the shorter arm 55 rlxed tothe hub M by a sheet metal clamping member 5l'. The member 5l entends around the hub dsl with the ends slightly spaced and extending radially therefrom to receive the spring 55. Adjacent the hub it theA ends or member 5l may be tightly clamped together-'and welded, if desired, toY secure the member and arm 56 0i spring 55 to 'the hub Mi, but the'external ends of' member 5:7. are spaced apart sufficiently to. permity free radial movement of the1 larger arm 58 of spring 55..

The free end of arm 58 ofspring 5:5. extends through an opening in bearing plate 41 to. engage a ratchet wheel 59A and act as a spring pawl to advance the ratchet wheel during oscillation of the armature 43, and the ratchet wheel is. utilized to drive the clock gear train. Although the armature 43 will be oscillated at a practically constant frequency as. determined by the periodic energization of the electromagnet by the timing mechanism, it has been round that the rate of acceleration of the armature movement in re.- sponse to magnetic impulses will vary with variations in the applied-voltage. To avoid possible variations in the movement ci the clock gear train a constant driving force should be transmitted thereto and the teeth of the ratchet wheel 59 are therefore so arranged that the ratchet wheel will be advanced by the pawl 58 only on the return stroke of the armature under the iniluence of the spring 50 and the driving force will not be affected by any changes in Ythe streng-th of the magneticfieldbetween the poles 40 and 4I.

The ratchet wheel 59y issecured to. a driving worm G j'ournaled on a shaft 6| which is pressed into and supported by a post 62 on frame I0. An indexV or star wheel 63 is also secu-red to the worm 60 and is engaged by a detent spring B4 to prevent reverse rotation or any movement of the ratchet wheel and driving worm at times other than when these parts are being moved. in one direction by the spring pawl 58. As shown in Fig. l, the detent spr-ing 64 is. in the form of a coiled wire spring having one end (not shown) in abutment with the frame and the other end extended and bent to engage the toothed index wheel 63 with the intermediate coiled portion ec-v centrically supported on a rotatably adjustable member 65 to thereby provide for a slight peripheral adjustment of the bent end with respect to the index wheel. The member 65 is adapted to be locked in position and secured to the frame post 62 by screw 66.

The driving worm 60 engages a worm gear 61 on shaft 66 mounted on the frame I0 between bearing 59 and an adjustable bearing screw 10, and a worm on shaft 68 meshes with a worm gear 'l2 which is rotatable on the center shaft 'I3 and forced by a spring 14 through washer 15 into frictional driving engagement with a collar I6 iixed to the shaft. The center shaft 13 extends through the bridge and is provided with a groove l'! to receive one end 0f a hairpin type spring 'I8 which is mounted on the bridge by a pin 19. The other end of the spring '18 is engaged within an opening in bridge and the spring is so formed as to exert both side pressure and an end pull en the shaft 13 to take up any side or end play in the shaft.

The center shaft 3 extends through the frame plate I9 and is provided with the cannon pinion 59 and a hub 8| for the hour wheel 82. The reduction gear train between pinion 8|) vand wheel 32 is not shown but may be of any conventional :luz

form and preferably includes an idler gear and a reset mechanism for manually setting the position of the hands as shown in our above-identified application, Serial No. 604,386. The usual dial plate has been diagrammatically indicated 3..

at E3 and it will be understood that the hour hand will be mounted on hub 8| and the minute hand mounted on the end of center shaft 13.

A back cover 84, as shown in Fig. 2, is secured to pillars 235 on the frame l0 by screws 86, and if.,

the electrical connections, not shown, may extend through dust tight, insulated openings in this cover. The skirt of the cover 84 fits into a peripheral groove 81 in the frame ||J which may, if desired, be filled with a suitable cement to thereby completely seal the clock operating mechanism in back of the frame l0.

Referring now to the diagrammatic showing in Fig. the electrical circuit includes a storage battery 83 with one terminal connected to ground by the conductor 89 and the other terminal connected by conductor 99 to the electromagnet winding 9| and from this winding by conductor 22 to the contact arm 30. When the balance wheel contact 22 is in engagement with the upper uninsulated face of the ear 34 on arm 30, as shown in Fig. 5, the energizing circuit for the winding 9| will be completed through the hub i6 and hairspring I8 to ground 93. The electromagnet is provided with a second winding 94 in hifilar relationship with the winding 9| with this winding 94 short-circuited upon itself by the conductor 95 so as to function as a damping winding to reduce the induced voltages and practically eliminate all sparking at the contact 22 and ear 34 during operation.

The damping winding 94 is tapped at 96 and connected by conductor 91 to an arm 98 of a startswitch which may be manually operated to engage a disk 99 with arm 98 to connect this arm by conductor |00 to the conductor 89, and complete an energizing circuit from the battery to winding 94 through conductor 90. The tap 96 is placed off center on the winding 94 to obtain a differential between the two sections of that winding. The starting switch may be of any desired form butis shown as associated with the resetstem |0| of a setting mechanism for the clock such asis disclosed in our copending application Serial No. 604,386 so that the starting circuitwill vbe closed whenever the reset stem is being operated yto set they clock hands.

In Fig. 5, thel location ofA the balance wheel Il with respect to the poles 38 and 39 is shown as the` normal position of rest or equilibrium to which ,the balancefwheel is urged by the hairspring with the contact 22 resting upon the upper face of the ear Sof contact arm 30. When the battery circuit is closed with the parts in this position, the winding 9| will be energized to create amagnet-ic field through the poles 38 and 39 to attract -the balance wheel and rotate it in the counter-clockwise direction. The rim of the balance wheel is formed with cam-shaped lobes |02,v

|03 and |94 to provide a gradually increasing acceleration during normal operation as the balance wheel moves counter-clockwise and shortens the air gaps between the lobe |02 and pole 38 and the lobe |93 and pole 39.

After the balance wheel has moved counterclockwise through ta predetermined arc, the contact 22 leaves the ear 34 and the electromagnet and poles will be deenergized but the balance wheel continues to rotate in this direction until its moment balances that of the hairspring which then releases its energy to reverse the direction of rotation of the balance Wheel. On the return clockwise stroke the energizing circuit will not be closed as the contact 22 passes the ear 34 since it moves under the ear in engagement with the insulating plate 35. It will be understood that the balance wheel moves clockwise until its direction is again reversed by the hairspring and that thereafter the balance wheel will be sustained in oscillation by the hairspring and periodic magnetic impulses imparted thereto during arelatively small portion of the counter-clockwise movement. A

In the foregoing description of the automatic starting operation from the position shown in Fig. 5, it was assumed that the contact 22 would be in engagement with the upper uninsulated face of ear 34. Although this may be considered to be the normal stopping position, the balance wheel may stop its oscillation in such a position that the contact 22 is either in engagement with the insulating plate 35 or even slightly spaced from this plate on the under side of the ear 34. In this event the circuit for the winding 9| would not be closed and the clock would not start until the starting switch is manually closed to complete the circuit for energizing the winding v91|. i

When/the winding 94 is energized by closure of the starting switch the magnetic field through the poles 38 and 39 will rotate the balance wheel in a counter-clockwise direction to the position shown in Fig. 6 and-tension the hairspring. The balance wheel will then be magnetically held in this position of maximum magnetic attraction until the starting switch is opened whereupon the winding 94 will be deenergized and the hairspring will swing the balance wheel in a clockwise direction and normal operation will be resumed. If the starting switch is associated with the reset stem |0 l, the switch is so arranged as to be closed when the stem. is pulled out to engage the reset gears vand will be opened by the return oi the stem to'normal position after it has been rotated to set the clockhands.` Y Y Referring .now to 191225.17, the balance wheel has celia-714 been shown in an abnormal position which it may' assume on very rare occasions, when 'stoppedf in which the' contact 22V is abutting the edge of the ear 34 or insulating plate 35 on contactv ar'rn 30. This interference prevents` the balance wheel from moving in a oouriter=clockwis`e direction to be started in accordance with the above described operatiinis.V To facilitate tlii starting of the clock under this unsal c'nitio'n, 'the ifiri f tHe balance Wheel is provided with spaced ut'stand-' ing ears' |05, |05 and |01 Whici are so located and dimensioned triat when the eictromag-net is energized the balance Wheel will be' moved in a clockwise direction te move the Contact 22 away from the ear' 34 and relieve tle iiite'r'fe'rer"ice.v It Will be Seen from Fig'.l 7 that .iny tli-iS p'sitn 'the magnetic pull on the' ears |05 and |00 loyA the poles 38 and 39', respectively, when tli'efpeles are en; ergzed, Will cause 'a greater' rtativ effect than the pull on the lobes |02 and |03,A respectively,- to thereby moi/e thebalance Wheel a clockwise direction. Since the hairs"pr'iiigH tens 4^ned icy this clockwise movement, it Will svifing the Balance Wheel in a countereclockwie directini as' soon as' the electromagn'et is' deerirgizcl and normal operation Will loe'A resiie'd.

In the preceding description of of the balance Wlieelthere eeen to any function for tl'ie Iolev |0Ai oi t K the rimof the irlfalcevilieelaoi itfsli d`- loe noted that tliey' 'are never' in a posit attracted by the poles when tlie elect' is energized but are provided 'so tlffritV the cal nce Wheel Will loe'A symmetrical and can lie' properly balanced. Y

lt has heretofore 'eeen'- mnti'ed that the' lcalanc'e Wheel: i'ssliwn Fig.A 6- apos tin of maximum magnetic attra fi lint-it Willlbe ited that the Contact 22.- is not in ege ear 3e in tri-ispo of 'Elie balance Wheel.. iii/alieny the tala-nce Wheel: M" clockwise during norma-l"- operator the magnetic ux in the electromagnet and poles do et Stop abruptly' as soon' as'- thei co"'tact E23 leaves tlie ear to break tliee'nergizring A rci direte theI tir-ne lag of the circ In tle osiiiir-` s'h'ow'nin Fig. 6l the' mag e 1c ii has not" q'y and the loalarice veheel cor'itinies"r to rtate' terncloclvvse; s-'it-cle v'v liebe that the air gapsbetweenltlielolie BZadpole 38 and' the lobe iilii-andfpoleiifviilllog'ir-'Eoi iese and due to the shape ofi the ends f tl'ielobes' tlieie win' be a retard-mg'- puii 'o1 iux has completely'diel-dowa T tion` tends to control the amplitude i o cil lori of` the balance Wheel'under' cond wiel ly varying applied voltage sucllas o` ato'niotive ape plications due tov varlatlonsiY peiatre and rate of charge and'othercoditionsfaiectirigtlie condition of the; vt

To also compe e'or Wide variatis in bate' tery voltage tliee' e'etroragnet core'f poles-l and. and tno-'balance wneei It" are preferably made from` a li'igli permeability magnetic alloy such as nickel? steel Whiclr loeoriiesA magnetically saturated at relatively low appli'emag'netfomc# tive forces,v so that' theV magnetic circuitI for the timing mechanism'is saturated'- at low applied voltages 'andiariincrease in' VoltageWillnot affect the magnetic pullV on thefb'alancee Wheel sufiiciently -to changel the lia-lance f Wheell timing', to any appreciable-gements' It Will beunderstood thatf-ma1'ry' modi-cations in the details of constructionv asfdisclosed -here'in and the sreparatie#useofN cert'anfeatures are cone operatoridreef dow-n v coco-'f Y templated as coming Within the scope of the present invention as deiined in the claims appended hereto.

W e claim:

l. in an electric clock of the magnetic impulse type',I an electrcmagriety a pair of poles, a balance Wheel of magnetic material mounted for oscilla tion between saidv poles, a circuit to periodically energize said eiectrornagnet including coacting contact members controlled by the motion or said balance Wheel and adapted. to close said circuit during a portion 0i the movement of said calance Wheel in one direction, loces on the rim of said' balance wheel adapted, to cooperate with said poles when said electrcniagnet is energized to sustain said balance Wheel in oscillation, a start ing circuit to energize said electromagnet, a man-- ual switch inV said starting circuit, and project ing ears on' the rim o saidv balance wheel adapted to be attracted by said poles when said starting circuit is closed` to impart a starting movement to said' balance wheel'.

21. In' an electric clock having an electromagn'ct and timing mechanism for periodically energizing said electromagnet, a clock gear train in cir-ding av ratchet Wheel, and a ddriving mecha-- nisri' for sam. ratchet wheel including a pair poles on eleetrornagnet, bearing plates se# to sai poles, an armature having av shaft in said bearing plates; said being positioned between .said poles and adapted to be moved in one direction upon energiaticn of said elcctrornagnct with spring means to more' said armature in the opposite directicn wi magnet is cieenergized, spr'r g an having one secured to said arniatw with the free end oi saisi arm engaging within a slot in one of bearing plates to it the movement of i111.

c Wheel for' drivin' iii clock gear train responsive t'o periodic errL g' @tien of i electromagnet.

in an' elec-nic a frame, an electron a pair of poes, a balance Wheel of magnet-ic material ai igerl for oscillation beta-een said poles, a circ electromagnet and ing; tov pe close said circuit lin- "se to said balance wheel *ed to oscillate with said balance wliecl, a spring Contact erm engagea'ole intermittently by said oscillating contact, a U- l bracket having one leg secured to sait ne, ineens to secure one end o said contact arm' to the other leg of said bracketv with the free end of said arm extending toward said oscilletting' contact, incansto adjust the spacing of said bracket legs to position the free end.- of said Contact arfn in tnepatn oi movement of said Contact, and auxiliary spring means fixed to said otii'er leg of said bracket extending thereircin intoengagenient with said Contact arm at spaced positions tliere'along preventing excessive vibra tionv ofsaid spring Contact arm siii'asequent to earch disengagement by oscillating Contact.

4. In an electric clock cf the magnetic impulse type, an electioinagnet, a pair' of spaced poles, age-erally circular spoked balance`v wheel o' I'iiagi'i tic material mounted for oscillation between' said poles, a circuit periodically energiaing electronia'g-riet including ocntact eleriietsclosed-'responsive to motion of said balance Wlnee'lE diiring" a predetermined movement thereof in* one direction, the said` circuit" imparting a i magnetic impulse to said' balancer Wheel when closed, said balance wheel rim including circumferentially spaced lobes thereon of gradually increasing radii and formed to provide a shoulder at the trailing end of said lobes when said balance wheel is moved in said one direction, the lobe portions of said balance wheel rim moving past said poles responsive to the inertia of movement of said balance wheel in said one direction beyond said predetermined angular displacement of said balance wheel, that portion of the magnetic flux remaining temporarily within the poles after the opening of the electromagnetic circuitby said contacts acting on the passing shoulders of said lobes providing a magnetic retarding effect on movement of said balance wheel in said one direction after the said predetermined movement thereof.

5. In an electric clock of the magnetic impulse type, an electromagnet, a pair of spaced poles, a balance wheel of magnetic material having a generally circular rim including spaced lobes thereon of gradually increasing radius and formed to provide a shoulder at one end thereof, said balance wheel being mounted for oscillation between said poles, a circuit periodically energizing said electromagnet, coacting contact members controlled by the motion of said balance Wheel closing said circuit during a predetermined angular displacement of said balance wheel in one direction imparting a magnetic impulse to said balance Wheel when said circuit is closed, the lobe portions of the balance wheel rim moving past said poles responsive to the movement inertia of said balance wheel in said one direction beyond said predetermined angular displacement thereof, the movement of said lobes past said poles presenting the shoulders of said lobes beyond the poles whereby to receive from said poles a magnetic retarding eiTect on continued movement of said balance wheel in said one direction by that portion of the magnetic iiux remaining within the poles after opening of the electromagnet circuit by said contacts.

6. An electric clock of the impulse type as claimed in claim 5 wherein the poles of the electromagnet are provided with narrow ends facing the rim of said balance wheel spaced less than degrees relative thereto.

PETER R. CONTANT. RAYMOND H. SULLIVAN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,826,719 Battegay Oct. 13, 1931 2,008,338 Rodanet July 16, 1935 2,084,226 Strahm June 15, 1937 2,125,638 Hubert Aug. 2, 1938 2,183,062 Conrad Dec. 12, 1939 2,430,628 Whitehead Nov. 11, 1947 FOREIGN PATENTS Number Country Date 20,496 Great Britain of 1909 297,891 Great Britain Oct. 4, 1928 491,442 Great Britain Aug. 29, 1938 504,553 Great Britain Apr. 27, 1939 509,608 Great Britain July 18, 1939 855,412 France Feb. 12, 1940 

